1. Technical Field of the Invention
The present invention relates to a liquid crystal display device in which a large number of thin film transistors are arranged together with pixel electrodes, and particularly to a liquid crystal display device using an electrical field applied in the lateral direction.
2. Description of the Related Art
FIG. 1 is a plan view showing a TFT substrate of a conventional liquid crystal display device. FIG. 2 is a cross-sectional view taken along I-I of FIG. 1. First, the conventional liquid crystal display device will be described with reference to FIGS. 1 and 2. A scan line 2 formed of Cr film and a common wire 3 extending in parallel to the scan line 2 are formed on a transparent substrate 1. Subsequently, an insulating film is deposited on the scan line 2 and the common wire 3 so as to cover them. A drain wire 7 for supplying a pixel signal is formed on the insulating film so as cross the scan line 2 and the common wire 3. A drain electrode 8 as a part of the drain wire 7 and a source electrode 9 are connected to a semiconductor layer 6. The source electrode 9 constitutes a storage electrode 10 on the common wire 3, and extends to the center of each pixel to form a pixel electrode 11. The semiconductor layer 6, the drain electrode 8, the source electrode 9 and the scan line 2 below the semiconductor layer 6 constitute a thin film transistor as a switching element 21. Reference numeral 20 denotes a storage.
Subsequently, an interlayer insulating film 13 is formed on the insulating film 5. An upper pixel electrode 14 for applying an electric field to the liquid crystal and a shield common electrode 15 are formed on the interlayer insulating film 13.
At this time, the shield common electrode 15 shields an electric field leaking from the drain wire 7 into the display area of the pixel. The upper pixel electrode 14 and the shield common electrode 15 are formed by patterning the same layer on the interlayer insulating film 13. The upper pixel electrode 14 and the shield common electrode 15 are located to be nearer to the liquid crystal layer 200 than the scan line 2 and the drain wire 7, so that they are located at the uppermost layer as the wire layer and formed of a transparent material such as ITO or the like. The upper pixel electrode 14 is connected to the lower pixel electrode 11 through a contact hole 17 penetrating through the insulating film 13 in the vertical direction. The shield common electrode 15 is likewise connected to the common wire 3 as the lower layer through a contact hole 18 penetrating through the insulating film 13 in the vertical direction.
Thereafter, the upper pixel electrode 14 and the shield common electrode 15 are formed on the interlayer insulating film 13, and then the surface of the display area is covered by an orientation film (not shown) and subjected to a rubbing treatment to form a TFT substrate 100. Furthermore, a color filter (CF) substrate 300 is disposed so as to face the TFT substrate 100, and a liquid crystal layer 200 is sandwiched and held between the TFT substrate 100 and the color filter substrate 300.
However, the conventional liquid crystal display device thus constructed has such a structure that when an interlayer short-circuit occurs between the shield common electrode 15 and the drain wire 7, it is impossible to separate the short-circuited portion by laser cut.